drm: bridge: dw-hdmi: Implement DRM bridge registration

As an option for drivers not based on the component framework, register
the bridge with the DRM core with the DRM bridge API. Existing drivers
based on dw_hdmi_bind() and dw_hdmi_unbind() are not affected as those
functions are preserved with their current behaviour.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170117082910.27023-11-laurent.pinchart+renesas@ideasonboard.com